ZA200608143B - Mechanical device for the concentration of minerals - Google Patents

Description

® WO 20805/094999 PCT/EBE2005/000046

Artisanal equipment for the c—oncentration off ores

Field of the invention

The invention relates to equipment for the gravimetric concentration of ores ..

The invention relates more specif® cally to equipsment for the artisanal concentration of ores, opera.ting according to the knowwn principle of jigging, whiclhsw has a lightweight structure _, can be easily moved over the aground and allows a high p roduction capac=ity to be achie=ved, while ensuring the best recovery rate.

Prior art

Jigging is a well-knecown technique for the gravimetric concentration of solid materials comprising substances of different densitiees [for exampl e€, an ore stripeped of its components (nat_urally for alluvial and eluvi al deposits or after grindimmg), the cleansi.ng of soil pollu.ted with buckshot, or any o ther mixture of different mater-ials].

By convention, in the re st of this speczification, the “term “ore” means a solid material in thes state of parti cles of variable size and slmape, consisting of two or more minerals of different densi ties. The term “slurry” means: an aqueous dispersion or suspension of the ore in water- or another appropriate liqu=d.

In the jigging technique, a slurry is suabjected to a suczcession of cycles of altern.ately upward amd downward pulsees in a tank. A substan.tially horizont-al grille dividles the tank into two superimgpoosed compartmerats and the

. @

J WO 2005/094999 PCT/BE2005/000046 slurry to be processed is introduced irato the upper compartment. The totality of the particles of the slurry in the upper compartment of the tank is -~called “filter bed”. This b ed may consist of the various components of the ore procezssed or, as a variant, of an additional material, of intermediate density. During the pulse cycles, the slurry particles are subjected to brief accelerations which produce an alternating cycle of slurry expansion and particle settling. A continuouvas water upflow is commonly su -perimposed on the upward and downward pulses, with the function of adjusting the sucti on during the downward pulse s. Due to the combined effect. of the upward and downward pulses, a densimetric (or~ gravimetric) stratification of the ore particles takes place in the tank, accordin.g to their density: a dense fr-action settles in the tank an.d a light fraction is removed with the slurry by overflow fr—om the tank. The dense fract ion is divided into two sulofractions, according to th-e grain size distribution: the fine grains pass through the grille and collect in the bottom of the tank, whil-e the coarser particles are xetained by the grille and coll ect above it.

The ecjuipment used for implementimg the jigging technique is s-ometimes called a “jig”.

There is a high demand at the present time for jigs of lightweight design, suitable for artisanal production close to immediately processable ore deposits.

This type of artisanal equipment is partic ularly popular with gold washers, who are particularly at®tracted by the ease of movement of this equipment and its ease of operation. De2mand for this type of lightweeight artisanal equipment is also expressed by prospectors of very low- assay depositss, in which it is necessary to- analyze large quantities of -ore to obtain representative rezsults (this is

. @ ® WO 2005/094999 PCT/BE2005/0000~46 the case in prospectimg for diamonds, the useful content eof which is concentrated in a few stones).

In the documeent “Pan African Jicg - ConcentrateTur de minerais [ore conecentrator]” by Sicot&Hm, accessible eon the Internet site http://www.sicinter.corm, a jig meetimng the requirements sta ted above is descriloed. This knowwn artisanal equipment comprises a tank that a substantially horizontal grille divides into two superimposeed compartments. The equipment further comprises a device feor feeding the tank wi th an ore slurry and a device for generating the water pulse cycles discus sed above. This device consists of a piston or a membrarae, located undeer the grille and operated by adequate means. This known artisanal equipment mas the advantage of limited size; Dt can be easily moved, requires very littl e energy for ifs operation, and is compoatible with what can be provided by a man over a complete weorking day.

In this knowra artisanal equipment., the means use=d for separating the &ense and coarse-grained subfractiomn, collected above the grille, consists in coollecting it in a siphon installed insi de the tank, along t—he wall thereoZ=f.

A door that can be opesned from the outside is used to clear an opening made in th-e tank wall, opposite= the siphon, ard thereby to remove the: dense and coarse-grained subfracticon (or part thereof). Trhis extraction means is essentially a batch means, constituting a major drawback . In fact, it Hs not possible to predi.ct in advance the desnsimetric cut of the fraction taken an d, a fortiori, not pcossible to obtazin predefined or adjustable densimetric cut s. Furthermore, this batch extractiora means does not per-mit steady-statce operation during which the properties off the filter be=d remain constant. Mor eover, upon each operiing of the doom, a stream of slurry suddenly leaves the tank, and this

N C ) RAT SO 2 0% io) \ - oe

LEIA ; =, if ™ a T IA) ® WO 2005/094999 PCT/BE2005/0000D46 4 dissturbs the stratification of tke slurry in the tarak.

Thesse periodic disturbances of the slurry stratification in thes tank constitute a major drawback of this known equiipment, being particularly detrimental to its effectiveness, its productivity andl its energy efficiency.

This known equipment requires expert, skilled ard, cormsequently, costly personnel, thereby increasing t=he ope=rating cost.

The known artisanal equipement thus described is not— adaptable. In other words, its productivity is impossed by its dimensions and cannot be increased, thereby corstituting a further drawback of this equipment.

An additional drawback off this known equipment lies in its size, which cannot be r educed for transport.

Summnmary of the invention

The aim of the invent jon is to remedy the dr=awbacks of the known jig, describ ed above, by providincg a jig of novel design, which is specially adapted to art-—isanal production.

It is one object of the invention to provide a jig for artisanal production, in which the extraction of a derase fraction of ore does not cau se a disturbance in tthe str-atification of the slurry in the settling tank.

It is a further object= of the invention to provide a jig for artisanal produection, which allows, at wil_l, the densimetric cut of the dense fraction drawn ooff from the upper compartment of the tank to be adjusted.

It is a further object—= of the invention to

. @ ® WO 2005/094999 PCT/BE2005/000046 provide a jig for artisanal production, the operation of which is compatibl € with inexpensive manpcower.

It is arm additional object of the invention to 5 provide a jig for artisanal production, the operation of which only requires a moderate input of energy, while having high productivity.

It is &a further object of the invention to provide a jig for artisanal production, tHhe productivity of which can be optimized in each particulasr case, according to the ore process<ed, its origin, and the desired degree of concentration.

It is a further object of the invention to provide a substaratially multipurpose jig, which can be adapted easily to the ore processe=d so that its effectiveness is optimal in each particul ar case, even for low-grade ores, or those in which the denssity of the useful ‘material is not very different than that of the other ore components.

It is & further object of -the invention to provide a jig havimg all the above propert—ies, of which the weight and size are reduced, and which czan accordingly be conveyed easily to a production site.

In consequ ence, the invention rel ates to artisanal equipment for conceantrating ores, comprising: - a tank divided into an upper compartment and a lower compartment Boy a grille; - a device for feeding the upper compartment of the tank with an ore sIlurry; - a device for producing upwamrd water pulses through the grille ;

. @ - a device for extracting a dense and fine-—grained fraction of the ore from the lower compartment of tlne tank; - a device for extracting a dense and coarse- grained fraction of the ore from the upper compart ment of the tank, this device commprising at least one siphon which is located in the tank arid which communicates with at least one opening made in a =ide wall of the tank, abeove the grille; and - an overflow fom removing a light fraction of the slurry from the upper compartment of the tank, the equipment being char-acterized in that said ope ming in the tank wall discharges into a chamber, the upper end of which is located at a higher level than said overflow.

The artisanal ecuipment of the invention belongs to the category of equipment known by the term “j ig” and designed for concentrat ing ores, coal and other solid inorganic or organic matesrials by jigging. This teschnique is well known and its functional characteristics were discussed above.

The equipment according to the invent ion is artisanal equipment. Th<e expression “artisanal equipment” means equipment of lightweight and inexpensive desi gn, for which the investment, acquisition, maintenance and operating costs are with. in the scope of an skilled. worker (according to the defirmition generally given in French language dictionaries, particularly in Le Petit Recbert - dictionary of the Frencla language, Editions Dicticonnaires

Le Robert, Paris, June 2000, page 147), as opposed to industrial equipment that involves considerable investment and a large, highly traimed and costly manpower, ge=nerally beyond the scope of an iradividual of average affluemmce.

In the artisanal equipment according to the invention, the tank is tlhe receptacle in which the jigging

. @ ® WO 2005/094999 PCT/EBE2005/000046 iss performed. The shape of the tank is not critical. It m&Eay generally be prismaticz, or have a rectangular- or square cm-oss section. The tank is divided by a grille into two staperimposed compartments - The grille may be hor-izontal or okolique. The meshes of tlie grille are generally of uniform skape and size. They are preferably square, altlmough other shapes are compatible with the invention.

In the present specification, the expression “HF ine-grained fraction o=f the ore” means a grain-size fm-action whose particles have dimensions enablimg them to pass through the grille. The coarse-grained fra ction is a gmrain-size fraction whose the particles have dimensions larger than the meshes off the grille and are consequently st-opped by it. The grill e is sized according to= the grain s3 ze distribution desired for the dense and fi ne-grained fraction of the processecl ore. The optimum s#& ze of the grille accordingly deroends on various parameters, particularly on the ore processed, and may be easily determined by a person skilled in the art. The lower compartment of the tank or a part thereof advaantageously heas the shape of a hopper - The tank and the gril le must be meade from a material capalble of mechanically and chemically withstanding the slurries intended to circulate therein and the turbulence and abrasion forces generated by the pulsing off the water through the grille.

The device used to feed the tank wit h the ore sBurry is not critical for the implementation of the irvention. In one a_dvantageous embodiment of the irvention, the feed device2 comprises a channel im which the ore is mixed with water t—o obtain the necessary dilution.

TrHie channel is advantageowisly lined with a wear layer of a material capable of withstanding the abrasive action of the or—e poured thereinto. It may be integral with tlme tank or,

. @ ® WO 2005/094%999 PCT/BE2005/00004 6 as a vari ant, it may be removably attach_.ed thereto. It is preferably removable in order to decreasse the size of tlme artisanal equipment during transport. The use of a removable inlet channel serves to adjust their shape:, dimensionss and abrasion resistance, acccording to the ore:s processed . The use of a removable i nlet channel als © allows it- to be substituted with a di fferent feed, foex example, & chute or a screw conveyor.

T_he water-pulsing device is an e=ssential componerit for jiggimg. It is designed to project a stream of wate x upward though the grille of the tank at regular intervals , so that t’he slurry in the upper compartmeent of the tank i s subjected to a succession of cycles of alternately upwar d and downwzard pulses, as mentioned above. However, th e method of producing this device is not critical for the definitior of the invention. It may, for— example, compris e a pistorm traveling in an auxiliary chamber an d communicat-ing with the lower compartment of the tank, or a flexible rmembrane placed under the grille=, the central zon-e of the membrane being subjected ®o a controlle-d reciprocating movement.

Tke lower compartment of the tank comprises a device fom extracting a dense and fine-grained fraction o:f the ore. This device is not critical for- the design of thee invention and may, for example, comprise= a hopper blocked by a flap -

Tlie upper compartment of the tank communicatess with an owerflow that is located at a hig her level than thes grille. The overflow has the functioim of keeping the slurry levels in the tank substantially constant during normal ope=ration of the artisanal equipmuent. In a manne-x known per se, the fraction of the slurr-y that leaves the

® WO 2005/094999 PCI/BE2005/000046 tank via the overflow normally contains a light fraction of the slurry.

The device for extracting a dense and coarse- grained fractiom of ore from the tank is arn important constructive cornponent of the artisanal equipmnent of the invention. According to the invention, this extraction device comprises: - on ther one hand, a siphon that commurricates with 210 the upper part of the tank, this siphon discharoging into an opening made thr-ough the tank wall, above the gr-ille; and - on the other, a chamber which is loca-ted outside the tank, so that its upper end is at a higher level than that of the gril le. 45

The siphon is advantageously inside tlae tank and may then be formed by a vertical or oblique partition, immersed in the slurry, above the grille, facing the abovementioned opening. The lower edge of saie«d partition =0 is accordingly located above the grille, but at a level lower than that of the overflow, and the lower edge of the opening is locat ed at an intermediate level between that of the overflow and that of the lower edge of the partition.

Any other equiva lent device can serve as a siphon. =25

Said opening in the tank wall is partitioned so that the slurry from the siphon can flow into the chamber.

During normal operation of the artisanal equi pment, the pouring of the slurry from the siphon into the chamber does =0 not affect the slurry level in the tank, because the upper end of the chamloer is located at a higher levesl than the tank overflow.

In one particular embodiment of the artisanal =®5 equipment of the invention, the siphon comprises , as stated

. @ ® WO 2005/0949% 99 PCT/BE2005/0030046 above, a —vertical partition which, duming normal opera tion of the artzisanal equipment, is immersed in the slurry above the grilles, facing the opening made in the tank wall. In a preferred version of this embodiment, the partition As a vertically movable shutter facing said opening. “This version o f£ the invention serves to a-djust the density of the cut of the coarse-grained fracticon of the ore, 4d rawn off via tlhe overflow.

Duaring normal operation of the artisanal equipment of the in-vention, the dense and coarse-grained fractiom of the ore pmocessed progressively accumu lates in the chamber.

This must accordingly be periodically «drained of the or e it contains. In an advantageous embodimment of the artis anal equipment of the invention, an openwor_k basket is suspended in the chamber. The basket has the fwinction of collec ting the ore particles that fall into the chamber. It there fore suffices to raise the basket periodically in ordexr— to extract i t from the chamber and gather the ore that it contains, without adversely affecting the operation of the artisanal equipment.

Tlie artisanal equipment of th e invention is a jig intended =for artisanal production. I t can be designecd so that it i.s easily handled by a singl e person and carn be transportezd in light vehicles, on any type of road, and can be easily loaded onto aircraft of the= small carrier t—ype.

For this —purpose, in a preferred embodiment, the tank and its grill. e, the feed device, the overflow, the wa ter- pulsing dezvice and the siphon chamber form a coherent wIhole which is wmmounted on legs. The number- of legs is norm ally at least t—hree in order to make the as:sembly isostatic. In practice, at least four legs are generally used.

Ira one advantageous versiora of the prefe xred

. @ ® WO 2005/094399 PCT/BE2005/000046 embodimen® described above, the abovementioned siphon chamber i.s provided in at least one= of the legs of the artisanal equipment. It is preferable for said chamber and sald siphcon to be provided in each leg. This embodiment of the artis anal equipment has the advaritage of reducing its size and wweight and facilitating its =assembly.

Imm another embodiment, which is preferred, the artisanal equipment of the invention comprises four legs and the d.evice for extracting the demse and coarse-grained fraction eof the ore from the upper cosmpartment of the tank comprises : - on the one hand, four clmambers like the one defined ambove, each provided in a «different leg of the artisanal equipment; and - on the other, four siphons which communicate, each with a different opening made in. the tank wall, these four opemings each terminating in one of said four chambers.

The components of the artisamnal equipment of the invention are preferably made from 1 ightweight materials, which can withstand stresses on site. For this purpose, in one particular embodiment, the structure is made from epoxy/fibearglass laminate by the vacuum impregnation technique offering an excellent weiglmt/mechanical strength ratio.

Imm an additional embodiment of the artisanal equipment of the invention, this is formed from removable componentss allowing the rapid assembly and disassembly of said equipment. This embodiment of the invention is particulamrly well suited to lightweight and easily handled artisanal equipment, the tank then being able to serve as a receptacle= for housing therein the ot her components of the

- ® WO 2005/094999 PCT/BE20+05/000046 equipment, so as to minimize the volumes to be handleed.

In one pamrticular embodiment «—f the inventieon, the artisanal equipment comprises a second tank, placed downstream of the overflow. In this emmbodiment, the second tank is similar t-o the tank described above and, 1iIke said tank, also cowmpr ises a grille which divides it i nto an upper compartment and a lower compar—tment. This second tank is also connected to a water-pulssing device, whhich is designed in a mariner known per se to project a stmeam of water upward thre-ough the grille of the tank at —xreqgular intervals, so that the slurry in the upper compartrment of the tank is subjected to a successsion of cycles of alternately upwarcd and downward pulses , as discussed above.

This second tank is also equipped witlma at least one siphon terminating in a® least one chamber located outsi de the tank, as stated above. This embodime=nt of the in—vention serves to improve the ore production ydeld.

In a pereferred execution of the ar—tisanal equipment of the invention, the wvater-pulsing device comprises: - on the one hand, a flexible and sealed membrane dividing the lower compartment of the tarmak into two contiguous sukochambers; and - on the other, a membrarne-activating trmnember, designed to subject a central zone the=reof to a to-aand-fro reciprocating movement.

In this preferred execution. of the art%tisanal equipment of the invention, the flexi ble membrane may be vertical or oblique. It is preferabl e to use a ve=artical membrane . The membrane is also advarmtageously poszitioned so that the two subchambers have substantially equal volumes.

@ ® WO 20055/094999 PCT/BE2005/000046

For the implementation of t-he preferred execution descri bed above, the membrane may, f£or example, be mounted on a ~peripheral frame which is introduced into the lower

S compar—tment of the tank to form the= partition between the two abovementioned subchambers. In an especially advant ageous embodiment, a removable wall is fixed to the upper part of the frame, above the grille, to allow adjust ment of the discharge he#& ght from the first compar tment into the second. In this advantageous embodiment, the upper edge of said removable wall must be locate d below the overflow level.

In the preferred executiom defined above, the membrane may be activated by any adec—guate and known member.

A known member is advantageously used, associating a connecting rod-crank system. A member associating a connecting rod-crank system has tlae advantage of being manually operable using a pedal asse=mbly. This embodiment of the invention thus has the advantageous feature of being operab’le by an animal or a human be ing, without requiring any other drive power.

In an advantageous version of the preferred embodirmnent described above, the twwo subchambers of the lower compartment of the tank are prolonged respectively by two hoppers and the membrane-activat-ing member is located betweernr the two hoppers. This embod iment of the invention minimi=es the size thereof. It has the additional advantz=age of allowing the juxtaposittion of a second tank againstz the sill of the overflow, this second tank being similars to the first tank and compri sing a second membrane and an activation device thereof. By thus placing two or more teanks in series one after the other, each equipped with a membrane and a self-containesd membrane-activating

@ ® WO 2005/094999 PCT/BE2005/00004-6 device, the effectiveeness of the artisanal equipment of tlne invention can be -adjusted at will =and easily. The artisanal equipment according to this embodiment of tlnae invention is accordzingly a jig congisting of independerat modules of two or more juxtaposed tankss having their owan drive mechanism, whi ch can be assembled in series in ordear to increase the depoletion of ores that are particularly difficult to concent rate. This placing of several module=s in series serves to maximize the productivity boy controlling the reco—very in each caisson, which observes aan asymptotic distribut Don.

The artisana.l equipment of the invention has tlme advantage of being compact and having a high productivity=.

In general, for equ ivalent size, the pr-oductivity of thme artisanal equipment of the invention is at least 30 time=s greater than that obtained by conve ntional artisanal methods and allows foor higher recovery ra tes.

The artisana 1 equipment of the DAnvention has mamy applications. It has one particular application fox concentrating soil or ores occurring naturally in tke granular or powder- state, as for «example, alluvial products. The artdsanal equipment of the invention i. s especially appropriat-e for deposits of tlmis type located in geographic areas of difficult access, for examples, geographic areas re-mote from communication channels, a_s many exist on the A.frican continent, particularly in th_e

Democratic Republic of Congo. The artissanal equipment o=f the invention has a_ very particular apeplication for th_e artisanal concentrat ion of ores, gold, diamonds, or any valuable mineral, of different density t—o the environmen_t (cassiterite, wolfr-amite, coltan, touvarmaline, garnet , chrysoberyl, spinel, zircon, tanzanite, rhodonite, ruby, sapphire, etc.).

® WO 2005/094999 PCT/BE2005/000046

Brieaf description of the figures

The figures presented repreesent one embodiment of the invention.

Figure 1 shows a vertical and longitudinal cross sect=ion of a schematic embodim ent of the artisanal equipment of the invention.

Figure 2 shows a cross sect—ion along the plane II-

IT of Figure 1.

Figure 3 is a planar view of a preferred embodiment of t—he equipment according to the irwvention.

Figure 4 is a vertical cross section along the plarme IV-IV in Figure 3.

Figure 5 is a perspective view of the artisanal equi pment in Figures 3 and 4.

Figure 6 is a large-scale ~wiew of a detail of the equi_pment in Figures 3 to 5.

Figure 7 shows the equipmen t in Figures 3 to 6, in a ve=rtical and longitudinal cross section.

Figure 8 is a 1large-scale= view of a detail in

Figu.re 5.

In these figures, the ssame reference numeral denoetes the same element.

® WO 22005/094999 PCT "/BE2005/000046

Detaailed description of particular embodiments

The equipment shown in Figures 1 and 2 comprises a tank (1) equipped with a substantially horizomntal grille (2) .

The grille (2) divides the tank into two compoartments: an upper compartment (3) ancl a lower compoartment (4).

An inclined chanmel (5) discharges intc> the upper compoartment (3). It serves as an inlet for an ore slurry to koe classified.

The upper compartment (3) communicate=s with the ovemflow (6), which is located at a lower level to that of the upstream end of the channel (5).

The lower compartment (4) is prolonged downward by a hopper or hutch (7) blocked by an appropriate valve (8).

During the operat ion of the equipment ion Figure 1, the channel (5) is fed with ore of specified grain size distzribution, at an adequate flow rate. The lat ter must be dete=rmined by a series of prior tests, because it depends on the ore processed. A water feed (not showwn) dilutes thiss ore in order to obtain a feed-slurry diluti on of about 1/1 (by weight).

The slurry water fills the entire tank (1), up to the overflow (6) level. The ore particles peneetrate into the slurry.

A suitable pulsing device, not shown ir Figure 1, but well known in the jigging technique, subject s the water

- @ ® WO 2005/094999 PCT/BE=X2005/000046 i” of the lower compartment (4) t-—o upward pulses, wh ich expel it through the grille (2), int=o the upper compartment (3).

These pulses generate a cycle of alternating flui dizations and settlings of the slurry , which has the r—esult of stratifying the solid particle s of the slurry in the upper compartment (3): the densest _particles penetrate into the filter bed and reach the gri.lle (2). The densse grains smaller in size than the gril le mesh pass throucgh it and fall into the hutch (7) whe=xe the valve (8) =serves to extract them.

The dense grains, re=jected by the gri_lle (2), accumulate thereon and the s lurry is thereby s tratified into layers of increasing density.

The light fraction off the slurry, of wwhich the grains do not reach the gril le (2), is removed from the tank (1) via the overflow (6).

During said water pullses, it is recommended to control the suction effect dwmring the settling pohases by means of an auxiliary water feed (9) under the gri lle (2).

The dense grains which accumulate on the grille (2) must be removed therefrom. According to the i mvention, this removal is performed in a continuous and c¢ ontrolled manner, offering the great advantage of guaranteeli ng steady operation of the equipment. For this purpose, Whe upper compartment (3) comprises a s iphon (10), which c omprises, on the one hand, a vertical partition (11) immerseed in the slurry and, on the other, an opening (12) made th.rough the tank (1) wall. The partition (11) joins the oppos ite walls (13) and (14) of the tank (1.). Its upper edge= (15) is located at a level higher than that of the overflo.w (6) and its lower edge (16) is located above the gri_lle (2),

@ RE yar iy ® WO 2005/094999 P&CT/BE2005/000046 arranging a passage (M7) for the grains of oree accumulated on the grille (2).

The sill of th.e opening (12) is formed by the upper = edge (18) of a panel ( 19) which can slide vert ically and in a sealed manner along the wall of the tank (1). Said edge (18) is normally loca ted at an intermediate level between those of the sill (é6» and of the lower edge (16) of the partition (11).

The opening (C12) discharges into a chamber (20) located outside the tank (1). The chamber (20) has its upper end (21) located at a higher level thar that of the overflow (6) in order to prevent it from overf lowing.

Due to the pr essure generated by the thickness of the slurry in the upper compartment (3) , the dense stratified grains on the grille (2) are expe=lled through the passage (17) undesr the partition (11) &nd penetrate into the siphon (10). In the siphon (10), the grains are fluidized in the same way as those of the compartment (3).

Their level rises progressively to reach the equilibrium level which depends ora the density differentia 1 between the slurries in the compartment (3) and in the siphon (10).

The panel (19) is poszitioned under this slurry equilibrium level, for continuous removal of the grains which penetrate into the siphon (10). The height positioning of the panel (19) defines the ex traction rate from the siphon and thereby determines thes densimetric cut.

The panel (19 ) is positioned by mean.s of a winch (22) (or equivalent d evice), from which the poanel (19) is suspended via a chain (23). 3S A basket (24) placed in the bottom o=f the chamber

- @ ® WO 2005/094999 “PCT/BE2005_/000046 (20) serves to collect the gwmains of ore t—hat penetrate into said chamber (20) via the opening (12) . The koasket (24) is connected to a winch (25) via a clmain (26) , for periodic extraction from the chamber (20) and the=reby, recovery of the grains of ores accumulated therein. The walls of the basket (24) are p erforated to p-ermit the flow of water during its extraction from the chamber (20).

Before extracting the basket (24) from the ch _amber (20), it is advisable to raise the pan.el (19) to mommnentarily— stop the passage of the grains of o re from the siphon (10) into the chamber (20).

In one particular embodiment of the arta sanal equipment in Figures 1 and 2, the grille (2) represent=s the bottom wall of a shallow basirma, of which thes side wall is applied against the wall of the tank 1. This. embodiment of the artisanal equipment permi ts easy repla cement o f the basin. It also permits the use of the bamsin only, for example, to filter an ore brotla or slurry.

In the preferred embodiment of the in-vention, shown in Figures 3 to 8, the tank (1) is rectanegular. It is mounted on four legs (34), (35), (36) and (337), which are placed respectively at the fowur corners of the tank- (1).

The pulsing device comprises a vertical membrane (2:7) in the lower compartment (4) of the tank (1). The furnction and operation of the membrane «27) will be ex—plained koelow.

The membrane (27) is mounted in a frame (28X, in order to divide the compartment (4) int o two juxtapos ed subchaambers (29) and (30). The frame ( 28) 1s prolon-ged abov e the grille (2) in order to divide the upper ccompartmen_.t (3) into two juxtaposed subchamber-s (31) and (322). The upper edge (33) of the frame (28) is located at a lower level than that of the overflow (6).

- @ ® WO 2€05/094999 PCT/BE2005/000046

The two subchambers (29) and (30) are each prol onged by a hopper or hutch (7), equ-dpped with a valve (8). The two hutches (7) meet along the lower edge of the frame (28).

The channel (5) is a module that is clipped to the tank (1), so that its bottom wall is prolonged by the vert ical partition (11) that is vertical ly immersed in the subc hamber (31) of the tank (1).

The overflow (6) is prolongeed by an inclined channel (44) which is clipped to the tan k (1). The bottom wall of the channel (44) is prolonged by a vertical part ition (11'). The partition (11') is similar to the abovementioned partition (11) and forms a siphon (10’) in the wvicinity of the downstream end of the tank (1).

For the transport of the artissanal equipment in

Figures 3 to 8, the modules (5) and (44) are detached from the tank (1) and placed therein, in ord er to minimize the outs ide volume.

The artisanal equipment in Figure=s 3 to 8 comprises four- chambers (20), which are located r—espectively inside the four legs (34), (35), (36) and (37) . The siphon (10) accosrdingly comprises two vertical pane 1s (19) vertically movable in front of the corresponding oposenings (12) of the chambers (20) of the legs (34) and (36) (Figures 3 and 8).

Simi larly, the siphon (10‘) comprises t wo vertical panels (19 ) which are vertically movable in front of the corr-esponding openings (12‘) of the chambers (20) of the legs (35) and (37) (Figure 3).

In Figures 3 to 8, the membrane &27) has a circular shape. However, any other appropriate shape is suitable.

- @ ® WO 2005/094999 PCT/BE=2005/000046

The membrane (27) constitutes the pulsing devicee of the equipment. Fecor this purpose, a conraecting rod-cramnmk system (38) (Figures 4, 5 and 6) located ira the free spaces between the two hutch es (7) is connected tc> a pair of calkoles (39) and (40). Tine two cables (39) and (40) pass respgpectively on two returra pulleys (41) and are fixed respect—ively to the two sides of the membrane (27). The activaticon of the connecting reod-crank system (38) causes a teo-and-fro movement of tle membrane (27) which generates pulsees in the two lower subcchambers (29) and (30) of the tank (17).

In the equipment shown in F-igures 3 to 8, the tank (1) is formed by the juxtaposition of two caissons (42) and (43), between which the frame (28) of the membranes (27) is inserted (Figiare 3).

Duringr the operation of the artisanal equipment in

Figures 3 to 8, the ore to be proce ssed is poured into the inlet channel. (5), with water, to form a slurmy. The slurry enters the subchamber (31) off the tank (1), which is located above= the grille (2). The connecting =—xod-crank system (38) is activated perman.ently to dist-ort the membrane (27) and generate the pulses in the tank. The ore is progressively stratified in time subchamber (31), as stated above for the equipment in Figure 1. The dense fraction of tkie ore settles in the ssubchamber (31) reaching the grille (2 ). The fine particless of the dense fraction pass through -the grille (2), enteri:ng the lower swubchamber (29) and are collected in the hutcln (7) of the swmiubchamber (29). The co arse-grained particles of said dense fraction are retained on the grille (2), wkiere they prog—xessively accumulate. As in the case of the equipment in E'igure 1, these coarse-grained particles flow progressively into the siphon (10) a=nd, from there, into tZhe two chambers (20) of the two legs (34) and (36), whexrce they fall into the

- @ o WO 2005/094999 PCT/BE20055/000046 baskets (24). A less derase fraction of the slurry passes above the frame (28) up to the chamber (32). Ficgure 7 shows the distribution of the dense fraction of the ecre in the subchamber (31), abeove the grille (2). The= mean density of the part of th_is fraction which passes into the siphon (10) is higher than that of the part remain-ing in the subchamber (31), so t hat an equilibrium is estab lished defined by the mathematical equation:

Hy;.d; = h;.d, in which: d; denotes the m.,ean density of the ore in the chamber (31), outside the siphon (10); d, denotes the mean density of the ore in the siphon (10); h; denotes the hei ght of the overflow (6) abo-ve the grille (2); and h; denotes the h_eight of the sill (18) of the opening (12).

In the chamber (3 2), the slurry is also sul=jected to the pulses generated by the membrane (27). The dense particles that have not settled in the subchambem= (31) settle in the subchambem (32). The dense fine-ggrained particles pass through th e grille (2) and are collec=ted in the hutch (7) which is leocated below the subchamber- (30).

The coarse-grained parti cles which are retained oy the grille (2) accumulate thereon and pass progressively into the siphon (10‘) and, from there, into the chambers (C20) of the legs (35) and (37), where they fall into the oaskets (24). The fine-grained fr-action of the slurry passes above the sill of the overflow (6) and is removed via the outlet channel (44).

As described abov €, in the equipment in Figures 3 to 8, the tank (1) is fcormed by the juxtaposition of two

® ANS MERE ® WO 2005/094999 PCT/BE2005/(300046 caissons (42) and (43), between which the frame (28) of the membrane (27) is inserted. The two caissons (42) and (43) are assembled along juxtaposed flan ges (not shown), wwhich are cemented or bolted. The two cai ssons (42) and (43D may be of metal or of a synthetic resi_n. For a questicon of weight, it is preferable to make tlmem of synthetic resin.

This design of the artisanal equipoment of the invermtion permits a construction of compo-sites by the vacuum impregnation method and serves to incorporate the supoport of the drive mechanism (38) of the membrane (27) in these two caissons.

Claims (10)

1. @ ® WO 2005/094 999 PCT/BE2005/000046 CLAIMS

   1 . Artisanal equipment for concertrating ores, comprising: - a tank (1) divided into an upper «compartment (3) and a lower compartment (4) by a grille (2); - a device (5) for feeding the upper compartment of the tank =with an ore slurry; - a device (27, 38, 39, 40, 41) for pr-oducing upward water pul ses through the grille; - a device (8) for extracting a de nse and fine- grained f raction of the ore from the lower compartment of the tank; - a device for extracting a dense and coarse-grained fraction «of the ore from the upper compartmerat of the tank, this devi ce comprising at least one siphon (10) which is located in the tank and which communicates with at least one openimg (12) made in a side wall of the t=ank, above the grille; amd - arp overflow (6) for removing a light fraction of the slurrsy from the upper compartment of the tank, character-ized in that said opening (12) in the tank wall discharges into a chamber (20), the upper end of which (21) is located at a higher level than said overfl ow.
2. 2. The artisanal equipment as claimed in claim 1, characterized in that the lower edge (18) o.f said opening (12) can koe moved vertically.
3. 3. The artisanal equipment as claime=d in either of claims 1 and 2, characterized in that the tzank (1), the feed device (5), the overflow (6) and the si phon (10) form a coherent whole, mounted on legs (34, 35, 36, 37) and in that the chamber (20) is provided inside one of said legs.
4. 4. The artisanal equipment as claimed in any one

   &@ ® WO 2005/094999 PCT/BE2005/ 000046 of claims 1 to 3, characterized in that the siphon (10) comprises a substant-ially vertical paartition (11) amd in that the feed device (5) comprises an inclined channel , the bottom wall of which is connected to =said partition o f the siphon.
5. 5. The artisanal equipment as claimed in cla im 4, characterized in that the channel (=) and the part ition (11) form a removable coherent whole.
6. 6. The artissanal equipment a s claimed in anZy one of claims 1 to 5, characterized in tliat the water-pu lsing device comprises, on the one hand, a. flexible and s ealed membrane (27) dividing the lower cormmpartment (4) of the tank (1) into two coontiguous subchamlwers (29, 30) aned, on the other, a membrarae-activating memloer (38, 39, 40 , 41) designed to subject aa central zone of the membrane to a to- and-fro alternating movement.
7. 7. The artisanal equipment a= claimed in cla im 6, characterized in that the tank i.s formed from two contiguous caissons (42, 43), between -which the membra ne is inserted.
8. 8. The artis-anal equipment as claimed in eith er of claims 7 and 8, characterized in that= the two subcha mbers (29, 30) of the lower compartment (4) of the tanks are prolonged respectively by two hopperss (7) and in that at least part of the membrane-activat ing member (38 ) is located between the t_wo hoppers.
9. 9. The artissanal equipment a s claimed in an=y one of claims 1 to 8, characterized in that the grille (2) constitutes at least part of the bot—tom wall of a basin which is placed remov-ably in the tank.

   _ ® WO 2005/094999 PCT/BE2005/000046
10. 10. ~The artisanal equipment as claiimed in any one of claims 1 to 9, characterized in that it comprises a plurality of tanks (1) mounted in series one behind the other, so thatz the overflow (44) of an upstmream tank is the feed device (®™5) of the tank located immediaEately downstream of the upstream tank.